[sdiy] VCO Cap Switch

Ian Fritz ijfritz at earthlink.net
Thu Jun 6 04:34:23 CEST 2002


At 10:00 PM 6/4/2002, Scott Bernardi wrote:
>The datasheet shows the LM319 spec'd at 36v max, same as a LM311.

True. But I found that to get full output swing I had to use a rather small 
(750R - 1k) pullup resistor. In my TRI oscillators this caused the chip to 
run quite hot, so I reduced the PS voltages. Tracking was then much 
improved. For a SAW oscillator this isn't a big issue.

>The LM311 needs
>a pullup resistor also, doesn't it?

Not that I can see.

Another issue with the 319 is that there aren't any good application 
schematics. I must say, I really don't know the proper way to connect the 
ground pins. I just hooked them to the - supply, but this actually violates 
one of the max ratings. May be this is why I had trouble with heating.


>I used the second comparator in the LM319 for the pulse output (sawtooth 
>on one
>input and PWM input on the other).

A good plan.

  Ian




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